Approximately 1.5 billion tires are produced and around 1.4 billion new tires are sold worldwide each year, with 300 million tires sold annually in the United States alone. Each of those tires will eventually end as end-of-life tires. It is estimated that one car tire per person is discarded each year in the developed countries, and that around 4 billion of tires have been accumulated in stockpiles around the world. Significant additional quantities of tires are disposed of by other, less organized means. Tire piles often provide breeding grounds for pests and insects such as mosquitoes, because their shape and impermeability allow them to hold water for extended periods. Waste tire stockpiles are difficult to ignite; however, once ignited, tires burn very hot and are very difficult to extinguish, often burning for years and resulting in considerable release of air pollutants, including particulates. Tires are not biodegradable, and thus can remain to present the above hazards for many years after disposal. Used tires thus represent an environmental hazard and their elimination is an important task for human civilization.
Policies concerning the management of scrap tires and in general of any waste follow a hierarchical approach, attempting to alleviate the environmental impact according to the following order: waste minimization, reuse, recycling, energy recovery, and landfilling. Legislation related to waste management is driving the search for economic and environmental mechanisms that can contribute to solve the waste disposal problem. Scrap tire disposal in landfills is banned in the European Union and highly discouraged in the United States. Therefore, material recycling and/or energy recovery would appear to have a high potential for the future. Efforts to eliminate scrap tire material by recycling and other methods have been ongoing for some time, with jurisdictions such as the European Union and the United States making a concerted effort to encourage more environmentally friendly disposal methods. New methods such as pyrolysis to extract materials from tire scraps have been developed, and shown considerable promise for recovering energy and economically useful products such as metal, gas, oil, and carbon black from the tire scraps. Nonetheless, the methods used thus far have failed to recover materials efficiently enough to make pyrolysis of tires a viable pursuit. As a result, over 18% of scrap tires in the United States are still cast into landfills.
Therefore, there remains a need for an efficient system and process for recycling and/or extracting material from scrap tires.